桥基取代2,7’-(乙烯基)-二-8-羟基喹啉类化合物的密度泛函理论研究

在B3LYP/6-31G(d)水平上对2,7′-(乙烯基)-二-8-羟基喹啉(2,7′-Ethq_2)及其6种桥基取代物的几何结构进行了全优化,探讨了取代基对分子的结构、电荷转移、前线分子轨道能级、能隙等方面的影响.采用含时的密度泛函理论(TD-DFT)研究各分子的气相及液相中的电子光谱,分析光谱的变化规律.结果表明,取代基的电子效应和立体效应对取代物的电子结构和电子光谱有重要影响,取代基重新调整了2,7′-Ethq_2的原子电荷布居,改变了前线分子轨道能隙,导致吸收光谱发生变化.氨基和氰基对2,7′-Ethq_2影响较为显著,吸收波长红移较大.此外溶剂的极性对其电子光谱也有影响,随溶剂极性的增大,硝基取代物的最大吸收波长发生明显的红移,其它取代物的最大吸收波长均发生较小的蓝移.

Density functional theory calculation of the vinylene-substituted 2, 7'-(ethylene)-bis-8-hydroxyquinoline

The structure of 2, 7'-(ethylene)-bis-8-hydroxyquinoline (2, 7'-Ethq2) and its six vinylene-substituted derivates were optimized at B3LYP/6-31g(d) level of density function theory. The effects of the substituent on molecular structure, molecular charge transfer, energies of frontier molecular orbitals, and energy gaps were investigated. On this basis, the absorption spectra for each molecule were calculated in gas and solvent respectively using time-dependent density functional theory (TD-DFT) by the B3LYP method with the 6-31G(d) basis set. The computed results indicate that the electron-donating/withdrawing capability and the steric effect caused larger perturbation on the electronic structures and spectra properties of the 2, 7'-Ethq2 derivatives. The substituent re-adjusted the contribution of atomic charges and then changed the energy gaps of 2, 7'-Ethq2. As a result, the absorption spectra of the vinylene-substituted 2, 7'-Ethq2 were changed accordingly. The CN- and NH2-substituents exert significant effects on the absorption spectra, and the max absorption wavelength exhibits noticeable red shifts. The solvent polarization introduces modest influence on the absorption spectra. The calculated max absorption wavelengths undergo a shift to different degree in the media. As the medium polarity increase, the maximum absorption wavelength of nitro-substituted 2, 7'-Ethq2 is quite large red shifting, but the small blue-shifted for 2, 7'-Ethq2 and the other derivatives.